In a surprise revelation, a McMaster study found that human embryonic stem cells – “the great grandmothers” of all the other cells in our bodies – build themselves a nurturing cocoon that feeds them and directs their ability to transform into other types of tissues. And by manipulating the products of this tiny, cellular placenta, it may be possible for scientists to prompt the stem cells to grow into desired tissues and organs, or to switch off tumour growth in cancers, says Mickie Bhatia, the lead study author.

The study shows that making replacement tissues to treat disease requires more than just the manipulation of the stem cell itself.

“You have to control the surrounding cells that govern this (transformation) process,” Bhatia says.

Bhatia says the major reason scientists study embryonic stem cells is for their potential to generate new types of tissues for transplant into damaged organs.